Trilaminar explosive composition and method of preparation



United States Patent 3,118,796 TRKLAMINAR EXPLQSEVE COMPGSETKGN AND METHQD (ll .QREPARATHON Knud Waldemar Nielsen, Qopenhagen, Denmark, as= signer, by mesnc assignments, to Lawrence D. Colliurn,

Mount Vernon, Nit.

No Drawing. Filed June 5, 1959, Ser. No. 825,860 6 Claims. (Cl. 14-8) This invention relates to explosives, including high explosives and less powerful blasting explosives.

Ammonium nitrate explosives containing a combustible carbonaceous material such as paraffin, coal or a niti'o compound or the like having low explosive value. For example, they have an explosive speed of about 3000 to 3500 meters per second and a Trauzl lead block value of about 300 to 350 cc. For certain purposes, for example, blasting coal, where a high explosive is not desirable, explosives of this character are advantageous but they are highly susceptible to humidity, their rate of transmission of explosion is so slow that oftentimes parts of the explosive do not explode, and they have poor adhesion qualities. Their poor adhesion makes them difiicult to use in inverted bore holes, that is to say, in bore holes which open downwardly, as for example, at the top or" a tunnel.

Ammonium nitrate is also employed with high explosives such as nitroglycerine, din'itrochlorhydrln, trinitrotoluene or mixtures thereof in gelatin form. Such explosives have high explosive speeds, for example, 6000 to 7000 meters per second and a high T rauzl figure, for example, 400 to 500 cc. However, they are hazardous to manufacture, transport and handle; they present a health hazard in manufacture because of their tendency to cause headache among workers; and they tend to become stiff when cold.

It is an object of the present invention to provide improvements in the art of explosives.

It is a particular object of the invention to provide an explosive which combines ammonium nitrate or other oxidizer with a high explosive such as trinitrotoluene; which permits greater safety in manufacture, transportation and handling; which permits the production of high explosives or less powerful explosives at will; and which is easy to manipulate, which is resistant to water and which adheres well to bore holes.

The above and other objects of the invention will be apparent from the ensuing description and the appended claims.

in accordance with my invention I start with an oxidizer, preferably ammonium nitrate, in the form of small particles. I coat these particles with an oxidizable material which is non-explosive (or which, if explosive, has a very low explosive quality), which can be melted at a relatively low temperature and which is oxidized by the oxidizer, thereby functioning as a consumer of oxygen. I then apply to the coated oxidizer an outer coating of high explosive material.

There is provided by this means a laminar or multilayer material in which an outer layer of high explosive (which is preferably an explosive such as trinitrotolu-ene which consumes oxygen from an external source) is separated from an inner core of oxidizer by an intervening layer of oxidizable material. This intervening layer competcs with the high explosive outer layer for oxygen. Therefore, by controlling the thickness of the intervening layer the rate of oxidation and the speed and power of the explosion can be regulated. The high explosive and oxidizer components may be interchanged with the latter (the oxidizer) on the outside and the form r (the high explosive) on the inside. However, I prefer to have the oxidizer on the inside and the high explosive on the outside. Among other things, with the oxidizer on the inside the end product is more water resistant.

The oxidizer may be of any suitable type, for example, potassium nitrate or sodium nitrate or a chlorate, but I prefer ammonium nitrate.

The high explosive is preferably trinitrotoluene but it may be other explosive material such as picric acid or even an oxygen enriched explosive such as nitroglycerin-e. The outermost layer of high explosive is preferably not applied in full strength but in diluted form, preferably in the form of a gelatin such as a collodion gelatin.

The intermediate layer is preferably nitronaphthalene melting at about C. However, l-nitronaphthalene melting at about 59 C. or Z-nitronaphthalene melting at about 79 C. may be used. Mixtures of these nitronaphthalenes with each other, or with l,3-dinitronaphthalene or LS-dinitronaphthalenc (which melt at about 144 and 217 C., respectively) may be employed. It is desirable that the melting point of the nitronaphtnalone be somewhere in the neighborhood of C., so that it can be rendered fluid at a conveniently low temperature, yet will be solid at room temperatures and somewhat above, e.g., 20 to 50 C.

Any other oxidizable organic material which is inert chemically (i.e., noncorrosive and not reactive with the other ingredients at normal temperatures), may be used which is solid at room temperature, which melts at a convenient temperature and which can be oxidized by the ammonium nitrate may be used for the purpose. Exampics are parafrin, naphthalene, dipheryl, etc.

in forming the laminar or concentrically layered composition of my invention 1 prefer the following procedure:

ire oxidizer is provided in the form of small granules, for example, about 1 millimeter in diameter. On the one hand, the granules should be large enough to coat effectively but not so large that the surface-volume ratio between the inner and outer layers is undesirably small. The oxidizable coating material is selected to melt at a reasonably low temperature, for example, about 163 C. so that the coating operations can be carried out at a moderate temperature, yet when th temperature is reduced to nor l, a firm solid coating will form.

This organic coating material is melted and raised some. above its melting point. The granules of 'zer are then agitated in the molten mass of oxidizable coating material to thorou hly coat them with the coating material. It is at th s stage, by c rolling the relative propo bus of oxidizer and of oxi able coating material, that one can exercize an importan control over the end product. That is to say, a more powerful or brisant explosive can produced by employing less of the oxidizable coating material, and a less powerful explosive can be produced by employing more of the coating material. if a greater quantity of oxidizable material is employed, and a thicker coat results, the coaction between tne inner core of oxidizing agent and the outer layer of high explosive is, of course, impeded and the power of the explosive is reduced. Qontrariwise by making t intermediate layer thinner the interaction of the oxidizer and the high explosive is facilitated and explosive is more powerful.

I then apply the outer layer of high explosive, which is preferably done in two steps by first coating with the high explosive in pure molten form, then with a further quantity of the high explosive in gelatin form. lie-tween these two steps it is advantageous to separate adhering granules by suitable means, such as gentle abrasion with wooden balls. Also, in the last step a combustible metallic powder, such as aluminum powder, may be incorporated in the coating material.

s) The following specific example will serve further to illustrate the practice and advantages of my invention:

Example I Moist ammonium nitrate as produced is dried and granulated to produce granules having a diameter of about one millimeter. The ammonium nitrate granules are then placed in a heated pan provided with a stirrer. The pan is heated to about 115 C. Then 2 to 5% of nitronaphthalene based on the weight of ammonium nitrate, the nitronaphthalene having a melting point of about 90 C., is added and mixed. The nitronaphthalene will, of course, melt. As stirring is continued the granules of ammonium nitrate are thoroughly and completely covered with a shell or layer of nitronaphthalene. The temperature of the pan is then reduced to about 80 C. to solidify the coating and about 2 to 20% e.g., trinitrotoluene, melting at about 74 C., is added and mixing is continued until the precoated ammonium nitrate granules (i.e., the granules of ammonium nitrate which have been coated with nitronaphthalene) are thoroughly coated with the trinitrotoluene. The temperature is then reduced to about 5 C. and the mass is placed in a rotary drum containing wood balls. The drum is rotated to cause a gentle abrasion and a separation of granules which are stuck together. Then about 2 to 10%, e.g., 5% of trinitrotoluene in liquid gelatin form and about 2 to 10%, tag. 5% of aluminum powder are added and the mixture is agitated. Approximately 2 to 10% e.g. 5% of fine, powdered activated charcoal or coal can be used in place of the aluminum powder. Percentages given are by weight based on the total composition.

The granular coated product thus produced can be used, for example, even in moist bore holes because the granules are resistant to water and because they have good adhesive properties. By reason of the fact that the oxidizer is in the innermost core and the oxygen consuming explosive and its gelatin carrier are in the outermost layer, with an intervening layer of nitrotoluene, the explosive speed can be regulated. The nitronaphthalene competes with the high explosive outer layer for oxygen. T herefore by varying the thickness of this layer the explosive speed can be controlled. Explosive speeds of 6 to 7 thousand meters per second and above can be produced and products having a Trauzl number of 525 cubic centimeters and an explosive transmission above 6 centimeters are readily available. The explosive is safe to manufacture, transport and handle; it is water-resistant and adhesive; and it can be used elliciently to pack downwardly opening bore holes.

I claim:

1. A method of forming an explosive preparation consisting essentially of (l) a high explosive component selected from the group consisting of trinitrotoluene, picric acid and nitroglycerine, (2) a normally solid oxidizable material which melts at a temperature between about 50 C. and about 100 C. and is selected from the group consisting of nitronaphthalene, paraffin, naphthalene and diphenyl, and (3) an oxidizer component selected from the group consisting of nitrates of ammonium, potassium and sodium, which method comprises providing the oxidizer component in the form of small granules, mixing and precoating said granules with 2 to 5 weight percent of said oxidizable material at a temperature above the melting point of said oxidizable material, reducing the temperatul"? of the precoated granules to solidify the coating of oxidizable material thereon, and then mixing and further coating the thus precoated granules with about 2 to 20 weight percent, based on the total composition, of the high explosive component, at a temperature above its melting point.

2. A method of forming a laminar explosive preparation consisting essentially of small granules with ammonium nitrate coated with nitronaphthalene which is solid at room temperature and melts at a temperature between about 50 C. and about C. as an intervening layer and coated on the outside with a layer of trinitrotoluene, which method comprises mixing and precoating said granules of ammonium nitrate with 2 to 5 Weight percent of said nitronaphthalene at a temperature above the melting point of said nitronaphthalene, reducing the temperature of the resulting precoated granules to solidify the coating of nitronaphthalene thereon, and then mixing and further coating of the thus precoated granules with about 2 to 20 weight percent, based on the total composition, of trinitrotoluene in molten form at a temperature below the melting point of the nitronaphthalene.

3. A method according to claim 2 wherein the resulting coated granules are further coated with a mixture comprising about 2 to 10 percent of trinitrotoluene in liquid gelatin form and about 2 to 10 percent of a powder of the group consisting of aluminum powder and powdered activated charcoal, the percentages being expressed by weight of the total composition.

4. A laminar explosive preparation consisting essentially of 1) an oxidizer selected from the group consisting of nitrates of ammonium, sodium and potassium, (2) a high explosive component selected from the group consisting of trinitrotoluene, picric acid and nitroglycerine, and (3) an intervening layer of normally solid oxidizable raterial selected from the group consisting of nitronaphthalene, paraifin, naphthalene and diphenyl and having a melting point at a temperature between about 50 C. and about 100 C., said oxidizable material in the intervening layer being present in an amount of about 2 to 5 percent based on the weight of the oxidizer, and said explosive material being present in an amount of about 2 to 10 percent based on the weight of the total composition.

5. A laminar explosive preparation consisting essentially of granules of ammonium nitrate having a diameter of about 1 mm., an external layer of trinitrotoluene, and an intervening layer between said ammonium nitrate and said trinitrotoluene layer formed of a normally solid nitronaphthalene having a melting point at a temperature between about 50 C. and about 100 C., said nitronaphthalene in the intervening layer being present in an amount of about 2 to 5 percent based on the weight of the ammonium nitrate and said explosive material being present in an amount of about 2 to 10 percent based on the weight of the total composition.

6. An explosive preparation according to claim 5 which further comprises about 2 to 10 percent of its total weight of a powdered material selected from the group consisting of aluminum powder and powdered activated charcoal.

References Cited in the file of this patent UNITED STATES PATENTS 850,589 La Motto Apr. 16, 1907 2,048,050 Baker July 21, 1936 2,136,205 Byers Nov. 8, 1938 2,371,000 Snelling Mar. 6, 1945 

4. A LAMINAR EXPLOSIVE PREPARATION CONSISTING ESSENTIALLY OF (1) AN OXIDIZER SELECTED FROM THE GROUP CONSISTING OF NITRATES OF AMMONIUM, SODIUM AND POTASSIUM, (2) A HIGH EXPLOSIVE COMPONENT SELECTED FROM THE GROUP CONSISTING OF TRINITROTOLUENE, PICRIC ACID AND NITROGLYCERINE, AND (3) AN INTERVENING LAYER OF NORMALLY SOLID OXIDIZABLE MATERIAL SELECTED FROM THE GROUP CONSISTING OF NITRONAPHTHALENE, PARAFFIN, NAPHTHALENE AND DIPHENYL AND HAVING A MELTING POINT AT A TEMPERATURE BETWEEN ABOUT 50*C. AND ABOUT 100*C., SAID OXIDIZABLE MATERIAL IN THE INTERVENING LAYER BEING PRESENT IN AN AMOUNT OF ABOUT 2 TO 5 PERCENT BASED ON THE WEIGHT OF THE OXIDIZER, AND SAID EXPLOSIVE MATERIAL BEING PRESENT IN AN AMOUNT OF ABOUT 2 TO 10 PERCENT BASED ON THE WEIGHT OF THE TOTAL COMPOSITION. 